Oxidative dehydroaromatization

Hu, B., Yang, Y., and Sayari, A. (2001) Non-oxidative dehydroaromatization of methane over Ga-promoted Mo/ HZSM-5-based catalysts. Appl. Catal. A, 214, 95-102. 

In this section we shall discuss an example that is described in detail in the literature [29, T40], An attempt was made to develop a catalytic process for the production of aromatics from olefins by means of an oxidative dehydroaromatization... 

Scheme 13-5 Catalyst planning for the oxidative dehydroaromatization of olefins (Eqs. 13-3 to 13-5)...

The electron impact positive ion spectrum of l,2,5-oxadiazolo[3,4-/]quinoline IV-oxide 46 shows the loss of N2O2 from the molecular ion, a process that must be followed by a substantial rearrangement to enable the observed loss of propyne-nitrile. This remarkable result apparently arises through a series of H-atom shifts which relocate the dehydroaromatic moiety in the heteroring (890MS465). 

Metal oxides on zeolites have also found use as redox catalysts. High-temperature (700-750 °C) dehydroaromatization of methane under nonoxidizing conditions has been explored with a number of zeolitic catalysts modified with transition metal ions. Although coke formation at these high temperatures is a problem, calcined molybdate-impregnated ZSM-5 shows unparalleled activity of up to 8 % methane conversion with 100 % selectivity towards aromatics. Surface studies of these Mo HZSM-5 catalysts indicate that M0O3 crystals are on the external zeolite surface [123]. 

We undertook to investigate the reaction of olefins with oxide-free carbon surfaces in the hopes that chemisorption would occur in ways which could be related to the known chemistry of aromatic free radicals and dehydroaromatics, and that suitable manipulation might provide routes to homogeneously functionalized surfaces. High surface-area carbon fibers were heated to approximately 1000°C under vacuum to remove the surface oxides (evolution of H2O, C02, and CO). The samples were cooled to room temperature and exposed to vapors of various different substrates. The quantity of substrate adsorbed was determined and corrected for the quantity of physisorbed material which could be pumped off at room temperature. Some typical results are reported in Table II. In certain cases the reactivity towards oxygen was redetermined after exposure to the organic substrate. 

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